This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. 100 57 657.5-34, filed in Germany on Nov. 21, 2000, the entire content of which is incorporated by reference.
An electrical wire has a metallic conductor enclosed by a sintered insulation containing one or more layers of an unsintered polytetrafluoroethylene-based winding tape that overlap in the edge regions, the winding tape having a planoconvex cross-section that is defined by a curved upper boundary line and a straight lower boundary line.
The insulation of electrical cable or wire needs to conform to a number of requirements. These requirements include dielectric properties, mechanical strength, resistance to extremes in temperature, etc.
An electrical wire or cable known in the conventional art is typified by DE-PS 32 14 447 to Eilentropp, which is equivalent to U.S. Pat. No. 4,791,966. In Eilentropp, unsintered winding tape produces insulation with a specified cross-section. Sintering of the polytetrafluoroethylene subsequent to the winding process results in a smooth outer surface comparable to those obtained through an extrusion process. Similar to an extruded insulating covering, this insulation made from a winding tape provides resistance to mechanical forces that could lead to tearing of the insulation.
However, there are applications of wire and cable, for example in aircraft and satellite construction, which make new demands with respect to mechanical strength in combination with dielectric strength that the conventional art insulation is not able to easily satisfy. That is, the conventional art insulated cable fails to provide the desired compactness, electrical isolation and smooth outer surface combined with the high mechanical strength and dielectric strength required for the vigorous conditions associated with aerospace applications.
An additional disadvantage associated with the conventional art arises from the labeling of wires, for example, by stamping in of identifying information. This labeling can cause damage to the surface of the insulation. This surface damage, in interplay with dirt or dust particles, water or oils, forms lubricating films on the surface of the insulation. The lubricating films can easily lead to corona discharge during operation and thus ultimately to short circuits in the wiring area.
The invention, in part, pertains to an electrical wire or cable that overcomes the disadvantages of the conventional art and satisfies the demands for high mechanical strength and dielectric strength while retaining compactness of the insulation and provides a continuous, smooth outer surface.
The invention, in part, pertains to an electrical wire composed of a metallic conductor having at least one layer of polyimide winding tape wound around the metallic conductor, a sintered intermediate layer around the polyimide winding tape, and at least one layer of polytetrafluoroethylene winding tape around the sintered insulator. The polytetrafluoroethylene winding tape has a planoconvex cross section having a curved upper boundary and a straight lower boundary. The outermost layer of polyimide winding tape has a bond with the polytetrafluoroethylene winding tape. The polytetrafluoroethylene winding tape can be sintered. The metallic conductor can be copper or copper alloy that is bare, tinned, silver-plated or nickel-plated.
The invention, in part, pertains using a fluoropolymer is to bond the adjacent tape layers. The fluoropolymer can be either melt-processable or not melt-processable. The polytetrafluroethylene winding tape of the insulation comprises polytetrafluoroethylene modified with no more than 2% by weight fluoromonomers. The maximum thickness of the planoconvex winding tape is between about 10 and about 100 xcexcm and a width of between 3 and 50 mm, preferably about 5 and 25 mm. The winding tape of polyimide can be coated on one or both sides with a fluoropolymer.
The invention, in part, pertains to a method manufacturing an electrical wire, which provides a metallic conductor, winds at least one layer of polyimide winding tape around the metallic conductor, forms a sintered intermediate layer around the polyimide winding tape, winds at least one layer of polytetrafluoroethylene winding tape around the sintered insulator, and bonds the outermost layer of the polyimide winding tape with the polytetrafluoroethylene winding tape. The method additionally sinters the polytetrafluoroethylene winding tape to produce a homogeneous sleeve with a smooth surface. The polytetrafluoroethylene winding tape has a planoconvex cross section having a curved upper boundary and a straight lower boundary.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.